16 replies to this topic

[kingjamez]

I just received a used ASI533MC Pro and it has some strange color balance issues. I've seen other threads about this camera showing a double peak of the histogram when taking flats. That thread was a bit of a disaster with really bad advice being given to the OP about flats that had nothing to do with his problem.

 

When I got my camera in, I started building a dark library and immediately noticed a similar effect. All of my bias and dark frames have a strong blue tint as seen here in this 20 second master dark. 

 

 

I couldn't find any settings to change this in either N.I.N.A or SGP using the native windows driver or the ASCOM driver. Finally, in the ASICap app, I found a color balance setting, this is the only place I've seen the setting.

 

When I click "default" it sets the blue to "95" and the red to "52", whatever those numbers mean. That results in a double peak histogram as shown in the ASICap software:

 

When I manually set both red and blue to "50" the three channels are all balanced.

 

After setting blue and red to 50, I went back to NINA and reshot the bias and darks and the result is as expected: Each channel has an equal amount of bias noise / dark current.

 

Any thoughts on what is going on? Why is blue set as default in the camera/driver to 95? What does 95 mean? Why is the color balance setting only accessible from ASICap?

 

I have an ASI183MC pro and it was balanced from the factory and I've never had to worry about this issue with it's bias or dark frames.

 

 

Edit for future peeps: 

The problem is that I was using the ZWO native windows driver which doesn't save the raw data coming off the camera... that's bad. Use the ASCOM driver instead.

-Jim

Edited by kingjamez, 23 May 2020 - 04:22 PM.

[albusmw]

Hi Jim,

 

the ZWO ASI SDK supportes setting the white balance by the 2 parameters

ASI_WB_R, R,//red component of white balance
ASI_WB_B, B,// blue component of white balance

which can be set in the natural driver.

 

The question is why some software does offer it and some does not.

I am not sure if the parameter are stored in the camera after power off (the name e.g. is permanent).

It would be interesing to contact the pre-owner and ask him ...

 

This is why I build all my software by myself :-)

 

Best regards

 

Martin.

[DrGomer]

double peaks can easily happy with LED or (indirect fluorescent lighting) for the source since the source it self has two peaks (or more).   I use NINA for flats and adjust the histogram so that no peak is too high or two low. 50% usually puts the strongest peak around 60% and the lowest around 45% for my LED panel.  Whether it is right to do or not, I will take the calibrated OSC flat, use PI to split the CFA channels, do a linear fit, then recombine. 

[DrGomer]

Oh, and I didn't bother with bias frames. Just matched darks for lights, and matched darkflats for flats. Then when calibration, I make sure I turn off calibration scaling/optimization.   
I checked my 533 flats and darks and they both had double peaks. But it all calibrates the lights just fine. 
This is what my 325sub, 120 sec, 100 gain master dark with the 533 looks like when debayered and stretched:

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Edited by DrGomer, 23 May 2020 - 03:24 PM.

[kingjamez]

double peaks can easily happy with LED or (indirect fluorescent lighting) for the source since the source it self has two peaks (or more).   I use NINA for flats and adjust the histogram so that no peak is too high or two low. 50% usually puts the strongest peak around 60% and the lowest around 45% for my LED panel.  Whether it is right to do or not, I will take the calibrated OSC flat, use PI to split the CFA channels, do a linear fit, then recombine. 

One shouldn't adjust flats or darks, that defeats the purpose. If color correction needs to happen, best to do that on the lights. I take it that's how you adjusted it when you owned this camera?

 

Note that I'm taking darks and bias frames, there is no light input.

 

-Jim

[kingjamez]

Oh, and I didn't bother with bias frames. Just matched darks for lights, and matched darkflats for flats. Then when calibration, I make sure I turn off calibration scaling/optimization.   
I checked my 533 flats and darks and they both had double peaks. But it all calibrates the lights just fine. 
This is what my 325sub, 120 sec, 100 gain master dark with the 533 looks like when debayered and stretched:

Good to know thanks! I think this is odd behavior, would be very interested to know if it's this camera specific, or applies to all ASI533's.

 

-Jim

[jdupton]

Jim,

 

   When you originally took your Bias and Dark frames shown in the original post, which capture program did you use?

 

   There have been several recent discussions of this issue both here on CN and on other forums. As Martin (@albusmw) mentioned above, it is due to a setting within the SDK. It seems some programs pick up the setting and apply it to the captured frames while others do not. (At least that is how I understood the discussions.)

 

   I will try to find a link or two to the discussions and add in in an edit.

 

https://indilib.org/forum/ccds-dslrs/6368-strange-bias-frames-with-asi294mc-pro-under-astroberry.html#51097

 

https://www.cloudynights.com/topic/708376-pixinsightasi294-question/

 

 

John

Edited by jdupton, 23 May 2020 - 03:48 PM.

[bulrichl]

This behavior was described in several CN threads before:

 

https://www.cloudyni...-white-balance/

https://www.cloudyni...si294-question/

 

It was also mentioned  before in my guide, see https://pixinsight.c...ibration.11547/ .

 

The problem is not that parameters are offered to change the color balance of the image displayed on the screen, the problem is that the modified intensity values are also saved to the FITS files. These files don't contain raw data any more!

 

Bernd

 

[kingjamez]

Jim,

 

   When you originally took your Bias and Dark frames shown in the original post, which capture program did you use?

 

   There have been several recent discussions of this issue both here on CN and on other forums. As Martin (@albusmw) mentioned above, it is due to a setting within the SDK. It seems some programs pick up the setting and apply it to the captured frames while others do not. (At least that is how I understood the discussions.)

 

   I will try to find a link or two to the discussions and add in in an edit.

 

https://indilib.org/forum/ccds-dslrs/6368-strange-bias-frames-with-asi294mc-pro-under-astroberry.html#51097

 

https://www.cloudynights.com/topic/708376-pixinsightasi294-question/

 

 

John

Hi John,

Great question! 

 

I used N.I.N.A. to do the captures and I used the native windows drivers. I used SGP only to see if i could modify any settings within SGP to help, but didn't try taking frames there.

 

I also hadn't installed the ASCOM drivers, but SGP required me to do so since it won't work with the native windows drivers.

 

With the ASCOM drivers in both N.I.N.A. and SGP, even with the "default" color balance settings (as set in ASIcap), the output is as I expect, balanced)

 

It appears that the native windows drivers are reading from the color balance setting, but the ASCOM drivers are not. Good to know! I'll be doing all my calibration frames using the ASCOM drivers now.

 

Thanks for the help in figuring that out.

 

-Jim

[kingjamez]

This behavior was described in several CN threads before:

 

https://www.cloudyni...-white-balance/

https://www.cloudyni...si294-question/

 

It was also mentioned  before in my guide, see https://pixinsight.c...ibration.11547/ .

 

The problem is not that parameters are offered to change the color balance of the image displayed on the screen, the problem is that the modified intensity values are also saved to the FITS files. These files don't contain raw data any more!

 

Bernd

Thanks for those threads. 

 

I'd seen the first thread, it's the one that had me banging my head against a wall with all of the misinformation in there. It happens way too often. 

 

I hadn't seen the second thread which contains what I discovered today: That the ZWO native windows driver is not to be used. Thank you for pointing me in the right direction!

 

 

-Jim

[Umasscrew39]

Something isn't right.  I have been using the 533 since it became available and I discussed this on the 294 thread some of you posted above.  I only am using Sharpcap to create master flats and darks now (never tried them using N.I.N.A or SGP) and then use them to calibrate my lights using PixInsight and they work fine.  So, it is not the cameras.  For flats, I have used both 50/50 and default 95/52 R/B white balance with no issues but they are different looking on the screen.   I get 4 peaks (white, blue, red and green) and depending on your filter, the screen could be white, or a tint of green, etc.  The key is to make sure no peak touches the left side of the histogram and I try to get the white peak in the middle of the histogram.  If I do that, the lights are perfectly calibrated.  Maybe I will try one of the other programs and see if I get what you are seeing but SharpCap makes this very quick and simple.  I also spoke with Robin Glover about this 50/50 vs 95/52 setting as I mentioned on the other thread about the 294.  Basically, while some color differences may occur, especially in some stars, the changes will be, for the most part, subtle..... which is what I am noticing.   

[kingjamez]

Something isn't right.  I have been using the 533 since it became available and I discussed this on the 294 thread some of you posted above.  I only am using Sharpcap to create master flats and darks now (never tried them using N.I.N.A or SGP) and then use them to calibrate my lights using PixInsight and they work fine.  So, it is not the cameras.  For flats, I have used both 50/50 and default 95/52 R/B white balance with no issues but they are different looking on the screen.   I get 4 peaks (white, blue, red and green) and depending on your filter, the screen could be white, or a tint of green, etc.  The key is to make sure no peak touches the left side of the histogram and I try to get the white peak in the middle of the histogram.  If I do that, the lights are perfectly calibrated.  Maybe I will try one of the other programs and see if I get what you are seeing but SharpCap makes this very quick and simple.  I also spoke with Robin Glover about this 50/50 vs 95/52 setting as I mentioned on the other thread about the 294.  Basically, while some color differences may occur, especially in some stars, the changes will be, for the most part, subtle..... which is what I am noticing.   

Whether it can be calibrated out, or if the affects are subtle doesn't really matter much. The problem is that the driver is changing the white-balance instead of just writing out the output of the camera. I don't want the driver changing anything for cosmetic purposes, that's my job. 

 

If there is no light coming into the camera, as is the case with a bias or a dark, there should be zero differences between the channels.

 

-Jim

Edited by kingjamez, 23 May 2020 - 09:29 PM.

[Umasscrew39]

Jim

 

Sorry I am not understanding your problem.  The driver isn't changing anything, at least in my case.  It is just writing out the output based on the settings and the subtle changes, I am referring to, if any, is in post-processing- not during calibration.  The camera is behaving exactly as it should (not getting what you are seeing), with flats and darks doing what they are suppose to do, with the resulting images looking very good.  

 

I hope someone can help you out.  Sorry I could not.

 

All the best.

[Umasscrew39]

Jim

 

I just wanted to share one more thing as this is just irking me as to what is going on.  Here are two screen shots from SharpCap of a 90s dark- one at 50/50 and one at 95/52 R/B white balance.  The screen is dark (not blue) in both cases and no distinct double peaks.  I was referring to only flats in my previous posts about the 4 peaks which you must have as light is coming in, of course.  This still does not explain the peaks you are seeing and the blue screen.  It would be curious if you try SharpCap and see if you get what I am or if your camera has an issue.

 

Apologizes in advance if I am still missing your point and issue with darks.

 

 

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[kingjamez]

Hi Bruce,

As noted, this problem was solved in post #9 no matter what capture program is used by moving to the ASCOM driver.

 

-Jim

[Umasscrew39]

HI Jim

 

Ugh!  I can't believe I missed that post.  I've never had this issue with darks or flats even though I have been seeing it pop up on multiple threads.  Sorry for wasting your time.

 

Bruce 

[kingjamez]

HI Jim

 

Ugh!  I can't believe I missed that post.  I've never had this issue with darks or flats even though I have been seeing it pop up on multiple threads.  Sorry for wasting your time.

 

Bruce 

No prob, that helps me figure out the context of your posts too! I should have lead the post with "i fixed it!" to make it a little more clear.